Among the drivers of the rapidly expanding use of the newer atypical antipsychotic medications (olanzapine, risperidone, quetiapine) is the claim that the atypical antipsychotic medications are associated with a lower risk for the development of tardive dyskinesia than are the older conventional drugs. Whether this claim is true is of great clinical, medicolegal, and pharmacoeconomic importance. Preclinical studies provide a credible rationale for why the newer atypical medications may have a lower risk of tardive dyskinesia than the conventionals; however, their lower risk has been addressed so far directly by only one published controlled efficacy trial and one study in the elderly. The purpose of the present application is to provide complementary data to these studies by using a naturalistic incidence study method. The current project proposes to investigate whether the incidence of persistent TD among patients taking atypical antipsychotic medications, alone or in combination with conventional medications, is lower than the incidence among patients taking conventional antipsychotics alone. In addition we will investigate other risk factors including affective disorder diagnosis associated with the incidence of TD in patients taking atypical antipsychotic medications and explore the prognosis and course of incident cases. To address these aims, a new sample of approximately 838 patients free of persistent TD will be recruited from the outpatient population of the Connecticut Mental Health Center (CMHC). These patients will be followed with biannual examinations for an average of 3.25 years. The CMHC was the site of a previous NIMH sponsored study (MH39665) that determined the incidence of new TD cases in the CMHC outpatient population from a sample identified between July 1, 1985 and December 31, 1986 and followed for up to 5 years. The existence of a previous sample at the same site provides a useful additional comparison group. Methods including sample ascertainment and TD assessment are closely modeled after the original work.